1. Field of the Invention
The present invention relates to a one-way clutch apparatus incorporated into an automatic transmission for an automobile.
2. Related Background Art
Generally, an automatic transmission for an automobile includes a planetary gear transmission mechanism having approximately third through fifth gears in addition to a torque converter classified as a fluid coupling, wherein a speed change is made by properly fixing or releasing components (such as a sun gear, a planetary gear, etc.) of the planetary gear transmission mechanism through a frictional engaging means such as a clutch, a brake, etc. The frictional engaging means incorporated into the automatic transmission involves the use of a wet type multiple disc in which frictional plates and separator plates are alternately disposed excluding some of band brakes. Press-fitting between these two involves using a pressure oil given from a variable speed control hydraulic circuit. Further, these frictional engaging means adopt some of mechanisms for actualizing facilitation of the variable speed control by having the one-way clutch built in an interior thereof and rotating a gear shaft, etc. in one rotating direction without any restriction.
FIG. 6 is a front view showing one example of a conventional one-way clutch apparatus incorporated into the frictional engaging means. FIG. 7 is an enlarged view of a portion E in FIG. 6.
A one-way clutch 1 comprises a cylindrical inner ring (an output shaft, an input shaft, etc. of an automatic transmission) 3, an annular outer ring 5 so disposed as to be coaxial with the inner ring 3 and rotatable relatively thereto, and a multiplicity of circular cylindrical rollers 7 defined as torque transfer members interposed between the inner ring 3 and the outer ring 5. An inner peripheral surface of the outer ring 5 is formed with a plurality of concave cams 13 each configured by a trough portion 9 and an inclined surface 11 that are formed in a circumferential direction, and with a plurality of concave grooves 15 formed in an axial direction. Each roller 7 is disposed between an outer peripheral surface of the inner ring 3 and the concave cam 13, and is biased by an accordion spring 17 against the inclined surface 11 within the concave cam 13. Further, an outer radially outwardly projected edge portion 21 of a block bearing 19 composed of an oil-retaining sintered alloy engages with each concave groove 15, and the block bearing 19 serves to keep an interval between the inner ring 3 and the outer ring 5. What is indicated by a numeral 22 in the drawings is an engaging pawl formed on the outer periphery of the outer ring 5. This engaging pawl 22 engages with an engaging groove formed in an inner peripheral surface of an unillustrated transmission-related element.
The outer ring 5 is fitted with a retainer 23 composed of a synthetic resin, which is configured by connecting a first annular flange 25 having a large diameter to a second annular flange 27 having a small diameter by columns 29, 31, 33, 35 extending in the axial direction. This retainer 23 prevents the rollers 7, the accordion springs 17 and the block bearings 19 from separating and coming off. For example, a couple of the roller 7 and the accordion spring 17 are interposed and held in between the columns 29 and 35 adjacent to each other, between the columns 31 and 33 adjacent to each other, and between the columns 33 and 35 adjacent to each other, and the block bearing 19 is interposed and held in between the columns 29 and 31 adjacent to each other. The numeral 37 in the drawings is a lip formed in the column 29 and engaging with a protruded portion 39 formed on an outer end portion of the block bearing 19.
In the conventional one-way clutch apparatus, the concave groove 15 with which the block bearing 19 engages is configured by the two side surfaces extending in the radial directions and the one bottom surface extending in the peripheral direction, and these surfaces are connected respectively by the circular arc surfaces. The outer edge portion 21 of the block bearing 19 engages with this concave groove 15, thereby keeping the relative interval between the inner ring 3 and the outer ring 5 and transferring the rotational motion. When the inner ring 3 and the outer ring 5 relatively rotate, the outer edge portion 21 of the block bearing comes into the surface-contact with side surface, extending in the peripheral direction, of the concave groove 15, and stresses generated due to a change in the relative interval concentrates on the concave groove 15, resulting in fatigue fractures in the outer end portion 21 of the block bearing 19 and in the concave groove 15.